ON THE ANATOMY OF FISHES. 
275 
areas of the lateral halves of the anterior chamber of the air-bladder in the Siluridse 
vastly exceed the areas of the external atrial apertures, and of the spatulate processes 
of the Scaphia which close them, and therefore, whatever may be the mode of motion 
or vibration of the former, the intensity of the final effect upon the latter must be 
increased in direct proportion to the difference between their respective superficial 
areas. Nevertheless, it is doubtful if any physiological significance can be attached 
to this resemblance which, after all, is merely superficial, and, as we have already 
suggested, is apparently conditioned by the necessarily large relative size of the air- 
bladder. On the other hand, the leverage of the Weberian ossicles in the Siluridm 
is very different from that of the Mammalian auditory ossicles. The approximate 
equality in the length of the two arms of the lever in the former case is sufficient to 
prove that no increased effect is gained in the transmission of any form of motion 
from the walls of the air-bladder to the auditory organ. In fact, so far from there 
being any special adaptations in the Weberian mechanism for this purpose, which 
would certainly seem to be necessary in the case of sound transmission, the facts of 
structure point quite in the opposite direction. The nature of the ligamentous 
connection between the different ossicles, and the fact that the movements of the 
Scaphia must take place in a plane at right angles to the posterior entrance of the 
cavum sinus imparls,* and the division of the neck of the sinus endolymphaticus into 
the right and left halves of the ductus endolymphaticus at right angles to the former, 
seem better adapted to diminish rather than intensify the effect produced on the 
auditory organ by slight vibrations or other movements of the walls of the air- 
bladder. 
id.) Hasse (18), in opposing the application of Weber’s theory to the Cyprinidre, 
lays some stress on the objection that the perilymph of the atrial cavities and cavum 
sinus imparis is contained within the interspaces of a reticular connective tissue, and 
therefore is ill adapted to transmit vibrations to the endolymph of the sinus 
endolymphaticus. This objection has considerable force when applied to the Cyprinidse, 
and possibly also to many other Ostariophysem, but is of little moment so far as the 
Siluridse are concerned. On this point we quite agree with Eamsay Wright’s 
remarks on the Siluroid Amiuriis catus, which ai’e in complete agreement with our 
own observations on Maci'ones nemurus. He says, “but in Amiurvs the fluid in the 
atrium and cavum is not imbedded in the meshes of the reticular tissue, the wall of 
the saccus endolymphaticus is so thin that any motion in the surrounding fluid must 
disturb its contents, and the currents so produced must certainly affect the neuro- 
epithelium as much, if not far more than the currents produced by sound waves ” 
(43, p. 385). Although this statement to some extent mitigates the force of Hasse’s 
objection in the case of one particular family, yet in all other cases the objection is a 
forcible one, and the exceptional condition of the Siluridae in no way lessens the 
* Hassk (18) directs attention to this point. 
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